It is well known in the electronic computer art that a computer system includes at least one printed circuit board commonly referred to as a mother board. In many applications, a plurality of daughter boards are connected to the mother board. Various connectors have been utilized in order to provide a reliable connection between the mother board and daughter boards. These connectors are generally referred to as edge connectors because they connect conductive areas located on the edge of the daughter boards with the mother board.
A preferred type of edge connector is the zero insertion force (ZIF) connector. This type of connector allows for easy insertion and removal of the daughter board from the mother board. This is an extremely important result, because it allows for easy replacement of defective parts of the system, which translates into a much more cost effective system.
A typical ZIF connector plugs into plated through holes of the mother board. Opposed rows of spring contacts, which extend away from the surface of the mother board, can then be cammed from an open position to a closed position. The open position allows the daughter board to be inserted into the connector under zero insertion force conditions, i.e. the conductive areas of the daughter board do not engage the contacts of the connector. This type of connector is essential when a daughter board, having numerous conductive areas, is to be inserted into a corresponding connector having numerous contact elements. Without a ZIF connector, it would be difficult to insert the daughter board into the connector without damaging the conductive areas of the daughter board or the contacts of the connector. Once insertion is complete the contacts are moved to the closed position, in which the contacts are in electrical engagement with the conductive areas of the daughter board.
The spring contacts are moved from the open position to the closed position by some type of camming means which is movable from a first position to a second position. One type of commonly used camming means is referred to as a linear cam. In a linear cam, each cam member is defined by a single plane. Therefore, as each cam member is moved from the first position to the second position there is no movement of that cam member outside of its original plane. There are many types of linear cams available in the market place today.
U.S. Pat. No. 4,636,021 discloses and describes a high density zero insertion force (ZIF) connector which utilizes a linear cam to move a portion of the housing of the connector, which in turn moves the contacts between the open position and the closed position. However, as the number of contacts needed is increased, the force required to move the contacts between the open position and the closed position is likewise increased. The result of the increase force has been the failure of many of the camming means. This is a direct result of the pivot between the cam lever and the cam arm having a vertical, as well as a horizontal force applied thereto.
U.S. Pat. No. 4,480,884 describes a linear cam which has slots provided in the cam members. These slots cooperate with pins to alleviate some of the forces on the actuator lever. Consequently, as the forces are distributed, the failure rate of the camming means is decreased. However, this type of camming means requires that the cam members be relatively wide in comparison the the connector, to ensure proper operation of the camming means. The slots must be of adequate length to ensure that vertical movement is not restricted. Consequently, such cam members are not practical when space is at a premium. To provide a narrow cam member with slots provided therein would result in failure of the cam member due to inadequate strength, as well as restricted movement.